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Posted by Simon on March 23, 2006, 6:34 am
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Hi, I'm cutting a 1 1/4 NPT thread in some 16mm thick aluminium. My tapping
chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
the hole first? Or should I just cut the thread in the straight hole?
thanks
Simon
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Posted by Jeff Wisnia on March 23, 2006, 12:47 pm
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Simon wrote:
> Hi, I'm cutting a 1 1/4 NPT thread in some 16mm thick aluminium. My tapping
> chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
> the hole first? Or should I just cut the thread in the straight hole?
>
> thanks
>
> Simon
>
>
>
Srtraight is what it takes.
The tap takes care of the taper.
It's the thread depth which "tapers", not the hole.
HTH,
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."
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Posted by Don Foreman on March 23, 2006, 6:54 pm
Please log in for more thread options On Thu, 23 Mar 2006 12:47:17 -0500, Jeff Wisnia
>Simon wrote:
>
>> Hi, I'm cutting a 1 1/4 NPT thread in some 16mm thick aluminium. My tapping
>> chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
>> the hole first? Or should I just cut the thread in the straight hole?
>>
>> thanks
>>
>> Simon
>>
>>
>>
>
>Srtraight is what it takes.
>
>The tap takes care of the taper.
>
>It's the thread depth which "tapers", not the hole.
>
>HTH,
>
>Jeff
Both the major and minor diameters taper on my NPT taps, Jeff.
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Posted by Jeff Wisnia on March 24, 2006, 10:57 pm
Please log in for more thread options Don Foreman wrote:
> On Thu, 23 Mar 2006 12:47:17 -0500, Jeff Wisnia
>
>
>>Simon wrote:
>>
>>
>>>Hi, I'm cutting a 1 1/4 NPT thread in some 16mm thick aluminium. My tapping
>>>chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
>>>the hole first? Or should I just cut the thread in the straight hole?
>>>
>>>thanks
>>>
>>>Simon
>>>
>>>
>>>
>>
>>Srtraight is what it takes.
>>
>>The tap takes care of the taper.
>>
>>It's the thread depth which "tapers", not the hole.
>>
>>HTH,
>>
>>Jeff
>
>
> Both the major and minor diameters taper on my NPT taps, Jeff.
Argh! I'll fall on my sword. I didn't say what I meant.
I was remembering having worked in a place where we tapped 1-1/4" and
1-1/2" female pipe threads in big runs of cast iron fittings and always
just used straight drills to size the holes before tapping.
But, Machinery's Handbook does say, "To secure the best results the hole
should be reamed before tapping with a reamer having a taper of 1/4 inch
per foot."
Jeff (Never too old to learn something.)
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."
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Posted by Randy Replogle on March 23, 2006, 4:19 pm
Please log in for more thread options On Thu, 23 Mar 2006 22:34:55 +1100, "Simon"
>Hi, I'm cutting a 1 1/4 NPT thread in some 16mm thick aluminium. My tapping
>chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
>the hole first? Or should I just cut the thread in the straight hole?
>
>thanks
>
>Simon
>
>
They tell me that there are tapered reamers for this but I've never
used one.
Randy Replogle
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> chart says 37.5mm hole, I'm wondering if I should use a tapered reamer on
> the hole first? Or should I just cut the thread in the straight hole?
>
> thanks
>
> Simon
>
>
>